System and method for relining sewer pipe sections with inspection capability

ABSTRACT

A system and process for relining conveyor lines like pipelines (1) with an internal inliner (2) and an external inliner (preliner 7), whereby the internal inliner (2) forms a stiffened internal pipe (30) after insertion into the external inliner (preliner 7) and the external inliner (preliner 7) is arranged at such a distance from the internal inliner (2) that an open flow section is formed between the internal and external inliners as an inspection chamber to detect and, where necessary, remedy leaks in one of the inliners, alternatively, a system and process with an internal inliner (2), a central inliner (3) and an external inliner (preliner 7) whereby the internal inliner (2) or the latter together with the central inliner (3) form a stiffened internal pipe (38) after insertion in the external inliner and whereby the external inliner (preliner 7) is arranged at such a distance from the central inliner (3) that an open flow cross-section between the central and external in liners is formed as an inspection chamber (9) to detect and, where necessary, remedy leaks in one of the inliners.

TECHNICAL FIELD

The invention relates to a system and a method for relining transportlines such as sewer pipelines or sections thereof, with an inspectioncapability.

Relining is a method of refurbishing damaged transport lines, generallylaid underground, by inserting a new interior pipe train or similarconstruction into the damaged existing line.

BACKGROUND ART

In a known relining method, a long train of weld-connected plastic pipessuch as polyethylene is pushed into the damaged sewer section. Since thepipes are generally inflexible, large excavations are required for thisprocedure.

In so-called short-pipe relining, short plastic pipes with a length ofabout 0.5 to at most 1 m are joined together in standard existingmanholes and, from this existing manhole, pushed or pulled into thesewer section being refurbished (DE-A 34 13 294).

It has been proposed (DE-A 27 04 438) to refurbish sewer pipes byinserting into the interior of the drain pipe a flexible pipeline whoseoutside diameter is smaller than the inside diameter of the drain pipe,whereby the flexible pipeline is positioned at a distance from the drainpipe to form a annular space. In this method, this annular space iscompletely filled with a hardenable, low-viscosity fill mass, such asmagnesium cement.

In DE-A1 39 30 984, a method is proposed in which a soft-PVC flexiblelining (inliner) is employed with a strong-threaded random-structurefiber outer layer of polyamide serving as a spacer. A rapid-hardeningmortar (so-called insulator) is inserted into the annular space formedvia the random-structure fiber layer between the sewer pipe beingrefurbished and the inliner itself and allowed to harden. A similarmethod is proposed in DE-A1 39 34 980, whereby HDPE (high densitypolyethylene) is one suggested material for the inliner.

In "Sonderdruck aus bbr 5/90; U-Liners; Protokoll einer Sanierung,Imbema Rohrsanierungs GmbH," a method of relining sewage channels isdescribed in which a continuous rigid HDPE pipe is folded at hightemperature during manufacture into a U-shaped cross-section and thisdeformed cross-section is secured with straps. This structure, which isstill quite rigid, is then pulled into the sewer and steam-heated underelevated pressure (about 1.3 bar) to the thermoplastic state, in whichthe HDPE pipe reverts to its original round cross-section.

Finally, in DE-U 90 12 003, WO 91/10862, and the company brochure"Steuler Umwelttechnik, Bekaplast fur Kanalrohre, 1989," a nubbedsealing sheet for relining sewage pipes is disclosed. This rigid HDPEinliner, however, can be used only for subsequent refurbishment ofpassable sewer pipes of large diameter.

DE-C 23 62 784 discloses a system in which a flexible fleece tube,plastic-coated on one side, is first saturated with resin and hardenersuch that the tube, after insertion by the inversion method into thepipeline being refurbished and after being pressed against the pipe wallby water pressure, hardens when heat is applied to the system, thusforming a new line system with a rigid pipe wall. Since theresin/hardener system in the carrier fleece has only a limitedprocessing time (pot time), the saturation process, transportation tothe site (in a refrigerated vehicle, if necessary), and insertion mustoccur within a relatively short time period. For refurbishing an entirepipe train, this system with resin-impregnated fleece is an adaptablesolution.

This method, however, can be used satisfactorily only for refurbishingpipes without relatively large cracks or pits, since these could allowthe resin to escape before hardening or since the new flow channel wouldotherwise exhibit unacceptably high unevenness. In a similar method(EP-A1 0 260 341), this disadvantage is avoided by first pulling anouter resin-impregnated flexible fleece tube into the pipe beingrefurbished, after which an inner flexible calibration tube, alsoresin-impregnated, is inserted by the inversion method into the outerfleece tube. Hardening of the resin results in a rigid new pipe that isno longer connected to the old pipe being refurbished. The use of tworesin-impregnated fleece tubes, however, makes this method verydifficult and expensive.

Despite the many proposed solutions for relining defective sewer pipes,there has up to now been no convincing system and method that permiteasy inspectability of the refurbishment process and the inliner.

OBJECT

The object of the invention is to provide a system and method whichfulfill these requirements.

DISCLOSURE OF INVENTION

The invention meets this objective through a system for re-liningtransport lines and a method preferably in conjunction with one or moreof the described preferred embodiments.

If the entire system consists of a total of two inliners, either theinside of the outer inliner (preliner) or the outside of the innerinliner has spacers which can take the form of, for example, ribs or astrong-threaded random-structure fiber layer in accordance with DE-A1 3930 984. However, the spacers are preferably formed by a plurality ofnubs, which are preferably 0.5-2 mm high, with a diameter of 3-30 mm andan average separation of 3-40 mm. The dimensions of these nubs are notcritical, since they serve merely to maintain a free flow cross-section.If the spacers are located on the outside of the inner inliner, theouter inliner (preliner) can, in the simplest case, consist of aflexible sealing tube which is smooth on both sides.

The inner inliner, which forms an inherently rigid pipe after insertioninto the outer inliner (preliner), can be formed by systems known in theart such as short-pipe relining, the U-liner method, soft lining, orinsertion of a continuous, heated HDPE pipe, etc.

Preferably, however, a system with a total of (at least) three inlinersis used. In this case, for example, after pulling in the outer inliner(preliner), a middle inliner is pulled into the preliner, whereby flatnubs serving as spacers are present on either the outside of the middleinliner or the inside of the preliner. However, the invention alsocomprises such embodiments in which the space between the middle andouter inliners, or between the inner and outer inliners, is formed by anadditional layer such as a liquid-permeable fleece, etc.

In accordance with a preferred embodiment of the invention, anadditional inliner is introduced into the middle inliner in a mannerknown per se, either by pulling or by the inversion method, whereby thisinner inliner, in accordance with a first embodiment of the invention,has a resin-impregnated outer fleece layer in the inserted state. Byinjecting a fluid such as water or air, the inliner is then inflated orerected, and if necessary pressed against the sewer wall, whereby theresin layer hardens and, in conjunction with the inner inliner, forms aninherently rigid inner pipe. Alternatively, the (subsequent) inside ofthe middle inliner and the (subsequent) outside of the inner inliner caneach have a resin-impregnated fleece, whereby the resin impregnationsreact with each other and harden, for example.

In accordance with another particularly preferred embodiment of theinvention, the outside of the inner inliner has means such as nubs whichserve not only to fix a defined separation (annular space) between theinner and middle inliners but also to provide a form-locking anchoringof the inner inliner in a hardenable mass, such as mortar, injected intothe annular space between the inner and the second inliners. Thisembodiment of the invention is described in more detail in thefollowing.

The inner tube-shaped thermoplastic inliner preferably has a wallthickness of 1.5 to 5 mm, whereby thicker walls can also be employed ifthe sewers being refurbished have a relatively large nominal diameter(for example, DN>1000 mm). Likewise, if the sewers being refurbishedhave small diameters (for example, DN 150 mm), thinner walls can bechosen.

The nubs on the outside of the inner tube-shaped thermoplastic inlinerpreferably have a diameter of 5 to 15 mm, a length of 8 to 20 mm, and ahead diameter larger than that at the base, to achieve an undercut. Thisnub form is generally known. The separation of the individual nubs fromeach other is about 1.5 to 4 cm, so that there are about 500 to 5000nubs per m².

The nubs serve on the one hand as spacers from the middle inliner, sothat, following insertion of the inner inliner into the middle inliner,a annular space is reserved between the middle inliner and the innerinliner. The individual nubs then extend into this annular space. Theannular space is completely filled with a hardenable mass such as asynthetic resin. The mass is then allowed to harden. A low-viscositymortar (insulator) is preferred as the hardenable mass.

After completely filling and hardening of this annular space withmortar, for example, the nubs with their undercuts form at the same timeanchoring elements which secure the inliner to the hardened mortar. Themiddle and inner inliners and the hardened mortar (insulator) therebyform a rigid (new) pipe, which is isolated from the outside by themiddle inliner and lined on the inside with the inner inliner.

In the mortaring process, the annular space between the middle and innerinliners is completely filled with the low-viscosity mortar. Ifnecessary, hardening of the mortar can be retarded or accelerated bytempering the fluid in the interior of the inliner. Through the use of ahigh-strength mortar, the filled annular space forms a load-bearingshell and thus simultaneously ensures the statics of the inliner. Afteronly 12 hours hardening time, for a nominal diameter DN 800, all stressanalyses required of self-supporting linings in accordance with IfBT("Richtlinie fur Auswahl und Anwendung von Innenauskleidungen mitKunststoffbauteilen fur Misch- und Schmutzwasserkanale, Anforderungenund Prufungen, 09.82") and ATV A 127 ("Richtlinie fur die statischeBerechnung um Entwasserungskanalen und Leitungen") are fulfilled.

If the refurbished pipeline is subject to particularly high mechanicalstress (statics), two inner inliners with outside nubs can also beemployed, whereby both resulting annular spaces are completely filledwith mortar, for example.

To produce the tube-shaped nubbed inliners, a sheet of suitablethermoplastic plastic is formed into a tube in a manner known per se,whereby one side strip of, for example, 3 to 10 cm width, preferablyabout 4.5 cm width, is overlapped by the other, parallel side strip. Inthe overlap area, the side strips are thermally welded, preferably witha double weld. The inspection channel formed between the two weldsserves in leakage testing of the welds. The weld thereby runsapproximately parallel to the longitudinal axis of the inliner.

It is especially advantageous if, in the area of the double weld, thereis at least one row of nubs between the two welds. The number of nubs(spacers and anchoring elements) per m² in the area of the weld shouldbe about the same number as in the area of the remaining sheet. In thiscase, the nubs, possibly in offset rows, are arranged parallel to eachother and to the longitudinal extension of the sheet, whereby a space ofabout 0.5 to 2 cm, wide enough for a weld, is reserved between each twoadjacent nub rows. For larger diameters of pipes being refurbished,multiple nubbed sheets can be joined together as necessary to form aninliner of larger diameter.

In accordance with these methods, the inliners can, if necessary, ineffect be tailored to various sewer diameters. The outer inliner(preliner) in this case has an outer circumference correspondingapproximately to the inner circumference of the sewer being refurbished.Likewise, the middle inliner has an outer circumference correspondingapproximately to the inner circumference of the outer inliner(preliner). The same applies to the inner inliner.

Even in the extremely improbable case that both the outer inliner(preliner) and the middle inliner are subsequently damaged and thatwater can thereby penetrate the mortar layer from outside, therelatively flexible inner inliner in this case is not pressed in, i.e.,it does not indent, since the nubs are held by the hardened mortar.Depending on the nub geometry, outside pressures of up to 3 bar can bewithstood before the nubs are drawn out of the pipe shell.

In the end, it is not significant in the present invention how theinherently rigid inner pipe is formed, as long as an open flowcross-section is reserved between it and the outer preliner to serve asan inspection space for detecting and eliminating leaks as required.

With the help of this free flow cross-section or inspection space,following the refurbishment or even thereafter, a leak can be detectedusing methods known per se such as applying pressure above or belowatmospheric pressure, suction or collection with a thin inspection tubeof liquids penetrating the inspection space, measurement of theelectrical resistance using a test probe, etc. If necessary, a leak solocated can also be sealed in a manner known per se by injecting ahardening and/or swelling means into the inspection annular space.

In accordance with a further preferred embodiment of the invention, ametal foil such as aluminum is imbedded in one of the employed inliners(outer inliner (preliner), middle inliner, inner inliner). This barrierfoil serves as a reliable barrier against permeation or diffusion ofchlorinated hydrocarbons, etc., which can penetrate the thermoplasticmaterial of the inliners. The barrier foil is preferably integrated intothe middle inliner.

In accordance with a preferred embodiment of the invention, alight-colored pigment is mixed with the plastic for the inner inliner toobtain a liner of light color. As a measure for the "lightness level" or"global reflectance," the so-called L value is determined from a dulledsample as per DIN 5033, Part 4 (spectral methods, light type C, 2°observation angle, geometry 0°/45°). An L value of 100 means that 100%of the incident light is (diffusely) reflected (ideal white). Theinliner in accordance with the invention preferably exhibits a globalreflectance of>30%, preferably>60% (L value>30 or>60, respectively).This significantly facilitates subsequent inspection of the refurbishedsewer using a video camera.

In accordance with an alternative embodiment of the invention, nopigments or carbon black are mixed with the thermoplastic plastic forthe inner inliner, resulting in a transparent or translucent inliner. Asa measure for the "global light transmittance," that portion of theperpendicularly incident light (380-780 nm) penetrating the sample(including the scattered portion) is measured. The global lighttransmittance of the inliner in this embodiment of the invention is>30%,preferably>50%. This enables subsequent inspection of the mortarsurrounding the inliner for the presence of relatively large cavities,air bubbles, or cracks, for example.

In general, the inliners according to the invention can, givensufficiently high flexibility, be inserted into the sewer section beingrefurbished by the so-called inversion method. Preferably, however, theinliners are pulled from a normally existing manhole(standard manholestructure) to the next existing manhole, whereby intermediate manholescan be also be bridged. For this purpose, the inliner can be foldedapproximately in a U or S shape and pulled loosely, including overrelatively small bending radii.

Preferably, the prefabricated inliners are spandrel-braced on a reel atthe manhole structure. By means of a deformation unit positioned overthe entrance opening, the inliner is folded into an approximate U shapeduring the pulling procedure, resulting in a cross-section reduction ofabout 50% compared with the original state, with corresponding loss ofrigidity. This enables the convenient use of an inserted PE pipe bendinside the manhole structure to redirect the inliner by 90° and insertit into the sewer pound. From the corresponding end manhole of the poundbeing refurbished, the individual inliners are then likewise pulled inby means of a redirection device.

It is particularly advantageous that the inliners do not have to beheated prior to being pulled into the sewer pipeline, i.e., that theycan be pulled at the ambient temperature.

In the preferred embodiment of the invention, the outer inliner(preliner) is first pulled into the sewer being refurbished. If theouter liner (preliner) has nubs, these are positioned toward the inside.The middle inliner, if applicable with the nubs toward the outside, isthen pulled into the outer inliner, and the inner inliner, with nubs onits outside, is then pulled into the middle inliner.

In this manner, a three-shell system of inliners is produced thatclearly can be augmented if necessary with additional layers (inliners),as long as the attendant cross-section reduction is acceptable.

If possible, the welds in each case should be positioned in the crownarea of the sewer pipe.

The relining system of the invention incorporates, in a previouslyunknown manner, such in part contradictory characteristics as:

high flexibility for simpler insertion of the inliner through existingmanhole structures,

high resistance to aggressive chemical media,

absolute impermeability to exfiltration and infiltration,

high inherent stability and mechanical strength, such as undermechanical stress from outside (earth movements) or subsequenthigh-pressure water jet cleaning from inside,

long operational life,

applicability even for pipelines which are not passable,

applicability even for non-circular sewer cross-sections, pipe bends,etc., or heavily damaged sewers with water intrusion from the outside,

low energy consumption and level of expenditure during laying,

low loss of cross-section,

protection against incrustation,

favorable cost,

capability for leakage inspection, and

capability for refurbishment.

The invention will be described in more detail on the basis of anembodiment and the drawings.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 shows a nubbed sheet for fabricating the inner inliner;

FIG. 2 shows the inner inliner following welding;

FIG. 3 shows detail X of FIG. 2 (weld);

FIG. 4 shows a longitudinal section of a sewer being refurbished, whilepulling in the preliner;

FIG. 5 shows a longitudinal section through a sewer being refurbished,during filling of the annular space (schematic);

FIG. 6 shows a cross-section through a refurbished sewer (alternativeembodiment);

FIG. 7 shows a cross-section through the refurbished sewer (detail Y ofFIG. 8 after the annular space filling);

FIG. 8 shows a cross-section through the sewer being refurbished, beforethe annular space filling;

FIG. 9 shows the attachment of the inliner at the end of the sewer.

BEST MODE FOR CARRYING OUT THE INVENTION

A sewer 1 with nominal diameter of 300 mm (DN 300) is to be refurbished.Sewer 1 has standard manhole structures 14 spaced every 60 m (FIG. 4).

To produce the preliner 7, a preparation consisting of

97% by weight HDPE (Vestolen® A 3512 Natur; Huls AG; modulus ofelasticity 590 N/mm²)

2% by weight (white pigment PMM 869, Polyplast Muller)

1% by weight HDPE (Vestolen® A 3512 R, Huls AG; containing carbon black)

is homogenized in a single-screw extruder known to those skilled in theart and extruded onto a rolling mill as a flat foil with a width ofabout 1 m and an average thickness of 2.5 mm. The rolling mill consistsof a first roll with flat round depressions and a second, smooth roll.In the gap between the rolls, the thermoplastic material is pressed intothe flat depressions. Removing the sheet from the roll yields a sealingsheet with nubs 8 with a height of 1 mm and a diameter of 8 mm. Aftertrimming the sheet on both sides to a width of 985 mm, the sheet isformed in a second work step into the preliner 7 with an outer diameterof 300 mm, whereby a double weld with an intervening inspection channelis created in the overlap area by thermal welding.

For the middle inliner 3, a three-layer HDPE sealing sheet withsandwiched aluminum foil 10 is employed as a permeation barrier. Weldingto the middle inliner 3 is accomplished as for the outer inliner(preliner 7).

To produce the inner inliner 2, pure HDPE (Vestolen® A 3512 Natur; HulsAG; modulus of elasticity: 590 N/mm²) is used.

This preparation is homogenized in a single-screw extruder and extrudedonto a rolling mill comprising a first roll with slightly conical holesand a second roll. In the gap between the rolls, the thermoplasticmaterial is pressed into the slightly conical holes. Removal of thesheet from the roll yields a sealing sheet 13 with nubs. The nubs, withan initial length of 13 mm, are then compressed at the head using asecond rolling mill comprising a steel roll and a rubber roll, with agap width of 12 mm, so that the individual nubs 4, compressed to alength of 10 mm, have corresponding undercuts 11. In the embodimentshown, the sealing sheet 13 is 3 mm thick. The nubs 4 have a length of10 mm and a diameter at the base of 5 mm and at the head of 8 mm.

The translucent (opaque) inner inliner 2 has a global lighttransmittance of 53%.

Preliner 7, middle liner 3, and inner liner 2 are each cut to a lengthof 60 m, inspected for leaks, and transported to the site on a cablereel. In FIG. 4, pulling the preliner 7 into the sewer 1 beingrefurbished is shown in more detail. The preliner 7 is pulled into sewer1 from the standard manhole structure 14. Using apparatus 15, thepreliner 7 is first folded into an approximate U shape and, by means ofthe cable 16, fed into the sewer 1 via the roller guide 17 and theredirection device 18.

After pulling in the preliner 7, the middle inliner 3 and the innerinliner 2 are pulled into the preliner 7 in the same manner (FIG. 4).Subsequently, at both ends of the inner inliner 2, the nubs 4 areremoved for a length of 10 cm. These nub-free ends 31 of the inliner 2are pressed on both ends against the sewer interior wall 21 using cutoffbags 19 and 20 and sealed off in this area (FIG. 5). Fill openings 22and outlet openings 23 allow the filling and removal of (possiblytempered) water 24 under defined pressure. At the same time, any leakagecan be detected in time by testing for a drop in pressure. By virtue ofthe water-related interior pressure of about 0.5 bar, the inner inliner2 is pressed against the middle inliner 3, which is pressed againstpreliner 7, which is pressed against the inner wall 21 of sewer 1,whereby the nubs 4 fix a defined annular space 5 between the sealingsheet 13 and the middle inliner 7. A low-viscosity mortar 6 (brand nameHC/HT Relining Injector, Huls Troisdorf AG) is injected into thisannular space 5 via the filling funnel 25. In the example shown, themortar 6 is injected at low pressure from the crown of the lowest pointof the sewer pound, whereby the mortar 6 is accordingly distributed bygravity within the annular space 5 of the slightly inclining sewer 1. InFIG. 5, the current mortar level 26 is depicted. Air can escape asnecessary from the annular space 5 through ventilation ducts 27 and 28,and at the same time the current mortar level 26 can be monitored. Wheninjecting the mortar 6, the interior pressure in the inner inliner 2 canincrease under certain conditions; this can be monitored and compensatedfor using overflow 29.

After mortar injection is complete, the mortar 6 hardens within about 7hours, whereby the hardening time can be accelerated or retarded bytempering the water 24.

After hardening, the mortar 6 forms a rigid, self-supporting pipe 12that is reliably protected from corrosion from the inside by the innerinliner 2 and from the outside by the middle inliner 3. The nubs 4provide anchoring of the nubbed sheet in the mortar pipe (FIG. 7).

Finally, as shown in FIG. 9, the inliner 2 is attached at both ends tothe manhole structures 14. For this purpose, a staticallyself-supporting, rigid HDPE ring 30 is inserted from the manholestructures 14 into the end of the sewer, whereby the nub-free ends 31 ofthe inliner 2, together with the end of the middle inliner 2 and the endof the preliner 7, are clamped between the HDPE ring 30 and the sewerinner wall 21. Furthermore, an inspection tube 36 provides access to theinspection space 9 between the outer inliner 7 and the middle inliner 3.As shown in FIG. 9, the middle inliner 3 is additionally welded to theouter inliner 7 at the inliner end, i.e., at the manhole structure 14(weld 37). A sealing band 32 of butyl rubber (double-sided adhesiveband) serves as a further seal between the inliner ends 31 and themiddle inliner 3. After insertion of the HDPE rings 30, the latter arewelded to the inliner 2 (weld 33). Finally, a semicircular-arc-shapedHDPE plate 35, fastened from the manhole structure 14 at the upper halfof sewer pipe 1 with dowels 34, is welded to ring 30.

The use of a nearly transparent inliner 2 permits reliable TV monitoringof the annular space 5, filled with mortar 6, so that, for example,large air bubbles can be detected in time.

In FIGS. 8 and 7, a cross section of an accordingly refurbished pipe isshown. Between the outer inliner (preliner 7) and the middle inliner 3,an inspection space 9 (outer annular space) is fixed by the nubs 8.

FIG. 6 depicts an alternative embodiment of the invention in which theinner pipe 38 is formed from a resin-impregnated flexible fleece tube.

LEGEND

1 Sewer pipeline, sewer

2 Inner thermoplastic inliner

3 Middle inliner

4 Nubs

5 Annular space

6 Mortar

7 Outer inliner (preliner)

8 Nubs

9 Annular space, inspection space

10 Metal foil

11 Undercuts

12 Inherently rigid inner pipe

13 Sealing sheet

14 Manhole structure

15 Apparatus

16 Cable

17 Roller guide

18 Redirection device

19 Cutoff bag

20 Cutoff bag

21 Sewer interior wall

22 Fill opening

23 Outlet opening

24 Water

25 Filling funnel

26 Mortar level

27 Ventilation duct

28 Ventilation duct

29 Overflow

30 Ring

31 Nub-free inliner end

32 Seal

33 Weld

34 Dowel

35 HDPE plate

36 Inspection tube

37 Weld

38 Inner pipe

I claim:
 1. A system for relining a transport line with an inner inlinerand an outer inliner,whereby the inner inliner forms an inherently rigidinner tube after insertion into the outer inliner, and whereby the outerinliner is spaced from the inner inliner such that an open flowcross-section is formed between the inner and outer inliners to serve asan inspection space suitable for detecting and repairing leaks in theinliners.
 2. The system of claim 1, wherein the spacing between theouter inliner and the inner inliner is fixed by nubs on the inside ofthe outer inliner or the outside of the inner inliner.
 3. The system ofclaim 1, wherein the transport line is a sewer pipeline.
 4. The systemof claim 1, wherein the material of the inner inliner contains alight-colored pigment so that the inner inliner is of a light color. 5.The system of claim 1, wherein the inner inliner is of a transparent ortranslucent material.
 6. A system for relining a transport line with aninner inliner, a middle inliner, and an outer inliner,whereby the innerinliner, or the inner inliner in conjunction with the middle inliner,forms an inherently rigid inner pipe after insertion into the outerinliner, and whereby the outer inliner is spaced from the middle inlinersuch that an open flow cross-section is formed between the middle andouter inliners to serve as an inspection space suitable for detectingand repairing leaks in the inliners.
 7. The system of claim 6, whereinthe spacing between the outer inliner and the middle inliner is fixed bynubs on the inside of the outer inliner or the outside of the middleinliner.
 8. The system of claim 6, wherein the transport line is a sewerpipeline.
 9. The system of claim 6, wherein the material of the innerinliner contains a light-colored pigment so that the inner inliner is ofa light color.
 10. The system of claim 6, wherein the inner inliner isof a transparent or translucent material.
 11. A method for relining atransport line with an inner inliner and an outer inliner,comprising:providing the outer inliner in the transport line inconnection with the inner diameter of the transport line, providing theinner inliner within the outer inliner such that an open flowcross-section is formed between the inner and outer inliner to serve asan inspection space suitable for detecting and repairing leaks in theinliners and such that the inner inliner forms an inherently rigid innerpipe after insertion into the outer inliner.
 12. The method of claim 11,wherein the inner inliner consists of thermoplastic plastic and issoftened by heating before or after being provided within the outerinliner.
 13. The method of claim 11, wherein one of the inlinerscontains a metal foil as a diffusion or permeation barrier tochlorinated hydrocarbons.
 14. The method of claim 11, wherein thetransport line is a sewer pipeline.
 15. The method of claim 14, whereinthe inliners are successively pulled into the sewer pipeline viaexisting manhole structures.
 16. A method for relining a transport linewith an inner inliner, a middle inliner and an outer inliner,comprising:providing the outer inliner in the transport line inconnection with the inner diameter of the transport line, providing themiddle inliner within the outer inliner such that an open flowcross-section is formed between the middle and outer inliner to serve asan inspection space suitable for detecting and repairing leaks in theinliners, and providing the inner inliner within the middle inliner suchthat the inner inliner, or the inner inliner in conjunction with themiddle inliner, forms an inherently rigid inner pipe after insertioninto the outer inliner.
 17. The method of claim 16, wherein the innerinliner is a flexible tube, the outside of which has a fleece with ahardenable resin, and the resin is allowed to harden after beingprovided within the middle inliner.
 18. The method of claim 16, whereinthe outside of the inner inliner has means for fixing an annular spacingbetween the middle and inner inliners, and wherein after provision ofthe inner inliner within the middle inliner a hardenable medium isinserted into this annular spacing and allowed to harden.
 19. The methodof claim 16, wherein one of the inliners contains a metal foil as adiffusion or permeation barrier to chlorinated hydrocarbons.
 20. Themethod of claim 16, wherein the transport line is a sewer pipeline. 21.The method of claim 20, wherein the inliners are successively pulledinto the sewer pipeline via existing manhole structures.